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Versions: 00 01

Network Working Group                                        T. Peterson
Internet-Draft                                            April 27, 2019
Intended status: Standards Track
Expires: October 29, 2019


  DNS over Transport Layer Security announcements using DHCP or Router
                             Advertisements
                       draft-peterson-dot-dhcp-00

Abstract

   This specification describes a DHCP option and Router Advertisement
   (RA) extension to inform clients of the presence of DNS resolvers
   with Transport Layer Security (TLS).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 29, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   2
   3.  The DNS over TLS Option . . . . . . . . . . . . . . . . . . .   2
     3.1.  IPv4 DHCP Option  . . . . . . . . . . . . . . . . . . . .   2
     3.2.  IPv6 DHCP Option  . . . . . . . . . . . . . . . . . . . .   3
     3.3.  The DoT IPv6 RA Option  . . . . . . . . . . . . . . . . .   3
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   DHCPv4 [RFC2131], DHCPv6 [RFC3646], and IPv6 Router Announcements
   [RFC8106] all provide means to inform clients of available resolvers
   using the incumbent DNS protocol for querying, however there is no
   means of specifying alternate protocols to perform DNS queries.

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

3.  The DNS over TLS Option

3.1.  IPv4 DHCP Option

   The format of the IPv4 DoT DHCP option is shown below.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Code     |      Len      |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   |                          DNS Servers                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Code:  The DoT DHCPv4 option (one octet)



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   Length:  Length of the DNS Servers list in octects

   DNS Servers:  One or more IPv4 addresses of DNS servers

3.2.  IPv6 DHCP Option

   The format of the IPv6 Captive-Portal DHCP option is shown below.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |          option-code          |           option-len          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                           DNS Servers                         |
   |                                                               |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   option-code:  TODO (two octets)

   option-len:  Length of the list of DNS servers in octects, which MUST
      be a multiple of 16

   DNS Servers:  IPv6 addresses of DNS servers

3.3.  The DoT IPv6 RA Option

   The format of the DoT Router Advertisement option is shown below.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |      Len      |                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
   |                                                               |
   |                          DNS Servers                          |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Type:  TODO (one octet)

   Length:  8-bit unsigned integer representing the entire length of all
      fields, in units of 8 bytes.  The minimum value is 3 if one DNS
      server is contained in the option.  Every additional DNS server
      increases the length by 2.  This field is used by the receiver to
      determine the number of DNS server addresses in the option.




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   DNS Servers:  One or more IPv6 addresses of DNS servers.  The number
      of addresses is determined by the Length field.  That is, the
      number of addresses is equal to (Length - 1) / 2.

4.  Security Considerations

   An attacker with the ability to inject DHCP messages could include
   this option and present a malicious resolver.

   TODO: Further risk and threat assessments.

5.  IANA Considerations

   TODO: This section must be updated after assignments have been
   issued.

   This document requires the assignment of an option code assigned
   under the "BOOTP Vendor Extensions and DHCP Options"
   [bootp-registry], in addition to an option code assigned under the
   "Option Codes" registry under DHCPv6 parameters [dhcpv6-registry].

   Also, an assignment for an IPv6 RA Option Type from the "IPv6
   Neighbor Discovery Option Formats" registry under ICMPv6 paramters
   [icmpv6-registry].

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

6.2.  Informative References

   [bootp-registry]
              "Dynamic Host Configuration Protocol (DHCP) and Bootstrap
              Protocol (BOOTP) Parameters", n.d.,
              <http://www.iana.org/assignments/bootp-dhcp-parameters>.

   [dhcpv6-registry]
              "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)",
              n.d., <http://www.iana.org/assignments/dhcpv6-parameters>.



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   [icmpv6-registry]
              "Internet Control Message Protocol version 6 (ICMPv6)
              Parameters", n.d.,
              <http://www.iana.org/assignments/icmpv6-parameters>.

   [RFC2131]  Droms, R., "Dynamic Host Configuration Protocol",
              RFC 2131, DOI 10.17487/RFC2131, March 1997,
              <https://www.rfc-editor.org/info/rfc2131>.

   [RFC3646]  Droms, R., Ed., "DNS Configuration options for Dynamic
              Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
              DOI 10.17487/RFC3646, December 2003,
              <https://www.rfc-editor.org/info/rfc3646>.

   [RFC8106]  Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
              "IPv6 Router Advertisement Options for DNS Configuration",
              RFC 8106, DOI 10.17487/RFC8106, March 2017,
              <https://www.rfc-editor.org/info/rfc8106>.

Acknowledgments

   TODO

Author's Address

   Thomas Peterson

   Email: nosretep.samoht@gmail.com























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